560 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Estimation of Ammonia. 



The ammonia is aspirated off by suction in the two test tubes for 10 

 minutes or longer according to the pump, or by blowing, and estimated : 



(a) By Titration with -osN Alkali. 



5 c.c. undiluted urine + a few drops of a solution containing 10 gm. 

 potassium carbonate and 15 gm. of potassium oxalate per 100 c.c. are put into 

 one test tube and the ammonia collected in 5 c.c. *i N HC1. 



() Colorimetrically. 



1-5 c.c. of diluted urine or i c.c. of undiluted urine + K 2 CO 3 and 

 Kox. solution as above are put into one tube and 2 c.c. of -iN HC1 in the other. 

 The remainder of the process is as described under total nitrogen. 



Estimation of Urea. 



(1) The urea is decomposed by heating with potassium acetate at 150-160 

 for -J-i hours. The exact temperature is ascertained by introducing a 

 tiny bulb containing mercury chloriodide. This is prepared by heating 

 together molecular proportions of mercuric iodide and mercuric chloride at 

 150-160 for 6-8 hours. The fused mass is powdered and kept dry. Small 

 quantities are sealed up in bulbs i mm. in diameter. 



i c.c. of undiluted urine is put into a Jena glass test tube containing 

 7 gm. of dry potassium acetate. This is dried by keeping it at 115 for 

 24 hours ; i c.c. of 50 per cent, acetic acid, a temperature indicator bulb and 

 a little powdered zinc are added. The test tube is closed with a rubber cork 

 carrying an empty calcium chloride tube (25 x 1*5 cm.) to act as a condenser, 

 and held by a clamp over a micro-burner. In about 2 minutes the mixture 

 begins to boil and the mercury chloriodide in the bulb melts showing a 

 temperature of 153-160. The boiling is continued for 10 minutes. The 

 flame is removed and the contents of the test tube are diluted with 5 c.c. of 

 water which is added with a pipette through the calcium chloride tube so as 

 to rinse down the sides. 



(a) By Titration with 'O2N Acid. 



The ammonia is aspirated into 10 c.c. of 'iN acid after adding 2 c.c. of 

 saturated caustic soda in the same way as described under the total N 

 estimation. 



() Colorimetrically. 



i c.c. of diluted urine is decomposed as described above and the am- 

 monia is collected in 2 c.c. of *i N acid. 



The rest of the procedure is as under total nitrogen. 



(2) It is easier to decompose the urea by means of urease and to carry out 

 the method as described on p. 136 in test tubes. 



(a) By Titration with 'O2N Alkali. 



i c.c. of urine + "25 gm. powdered soy bean are aspirated for J~| hour. 

 25 gm. of sodium carbonate are added and aspirated for J- hour. 

 The ammonia is collected in 5 c.c. of -iN acid. 



() Colorimetrically. 

 i c.c. of diluted urine are treated as above. 



The ammonia is collected in 2 c.c, of -iN acid and estimated in the 

 same way as under total nitrogen. 



